Sliding steps are used in order make it easier for people to board and deboard a passenger transport vehicle by bridging the gap between the vehicle and the platform edge for boarding and deboarding, such as a station platform edge. However, problems arise when the horizontal gap width varies and in particular when, with regard to the vertical direction, the height of the platform edge is not constant, but different from platform to platform. This is the case, for example, in international passenger transportation and national regulations on the height of these platform edges. In EP 1916156 A1, the parallel arrangement of two independently movable sliding steps is proposed in order to solve this problem. However, this is disadvantageous in that the constructional effort and the requirements with regard to the assembly space are comparatively high due to the doubling of the sliding steps. In view of these drawbacks, the inventors of the present invention set themselves the object of finding a solution for the above mentioned problem that is more economical with regard to assembly space and more cost-effective.